IDENTIFICATION OF THE GLYCOSIDASE INHIBITORS SWAINSONINE AND CALYSTEGINE B-2 IN WEIR VINE (IPOMOEA SP Q6 [AFF CALOBRA]) AND CORRELATION WITH TOXICITY

The polyhydroxy alkaloid glycosidase inhibitors swainsonine [1] and ca lystegine B-2 [6] have been identified as constituents of the seeds of the Australian plant Ipomoea sp. Q6 [aff. calobra] (Weir vine) by gas chromatography-mass spectrometry and by their biological activity as inhibitors of specific glycosidases. This plant, which is known only f rom a small area of southern Queensland, has been reported to produce a neurological disorder when consumed by livestock. The extract of the seeds showed inhibition of alpha-mannosidase, beta-glucosidase, and a lpha-galactosidase, consistent with the presence of 1 and alkaloids of the calystegine class. Histological examination of brain tissue from field cases of sheep and cattle poisoned by Weir vine showed lesions s imilar to those observed in animals poisoned by the swainsonine-contai ning poison peas (Swainsona spp.) of Australia and locoweeds (Astragal us and Oxytropis spp.) of North America. These results indicate that W eir vine poisoning is an additional manifestation of the induced lysos omal storage disease, mannosidosis, possibly exacerbated by inhibition of the enzymes beta-glucosidase and alpha-galactosidase by calystegin e B-2. This is the first reported example of a single plant species ca pable of producing structurally distinct glycosidase inhibitors, namel y, alkaloids of the indolizidine and nortropane classes.